LOS ANGELES — As the Mets close in on hiring Brodie Van Wagenen as their general manager, the MLB Players Association has significant concerns about one of the sport’s highest-profile agents going to work for a team in an even higher-profile role.

Van Wagenen and the Mets have an agreement in place, a source said Saturday, though he won’t be introduced until Tuesday at the earliest. If the World Series, which the Red Sox led 2-1 over the Dodgers heading into Game 4 Saturday night, goes seven games, the news conference will be Thursday, the source said.

When everything is finalized, the players’ union will be watching the situation closely.

“There has been a switching of sides throughout our history. It’s not the first time that it’s happened,” said Tony Clark, executive director of the MLBPA. “To the extent that in each instance that it does happen, are there things that we are concerned about? Yes. Are there things that we are going to be paying attention to? Yes.

“At the end of the day, making sure that the rights and the interests of the players are protected against the backdrop of someone who was in the representative community now being a part of management is something that we pay a lot of attention to.”

Van Wagenen, 44, is the co-head of CAA Baseball, whose clients include Jacob deGrom, Yoenis Cespedes, Noah Syndergaard, Brandon Nimmo, Todd Frazier, Robert Gsellman and Jason Vargas, plus Mets minor-leaguers Justin Dunn and Tim Tebow (though Van Wagenen doesn’t directly represent every player). Because of his prominent position with the company and his close relationships with his clients, Van Wagenen is privy to sensitive information about those individuals.

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That ethical gray area — one that Scott Boras, perhaps the only baseball agent more prominent than Van Wagenen, said would prevent him from making such a move — is what raises red flags for the union.

DeGrom is the most significant example in this scenario. In July, Van Wagenen made news by saying the Mets should sign deGrom to a quite lucrative extension or strongly consider trading him. As recently as the start of this month, when the phone first rang and the Mets were on the other end, Van Wagenen would have fought for every dollar for deGrom. Now he will be on the other side of the table, arguing against the righthanded ace and likely NL Cy Young Award winner, be it in long-term contract talks or in preparation for an arbitration hearing during the winter.

DeGrom is under team control for two more seasons and is scheduled to be a free agent during the 2020-21 offseason.

“To the extent that confidential information becomes less confidential, yes, that is a concern,” Clark said. “How players are treated, information that’s being provided that could adversely affect a player that he may be aware of based on [a previous agent-player relationship], all of that is a concern.”

In recent baseball history, there is one previous example of this sort of move: The Diamondbacks hired Dave Stewart as their general manager in 2014 (for two seasons).

Clark suggested that the union didn’t have to get involved as a result of Stewart’s previous role as an agent.

“We haven’t found ourself in a place, based on how the rules currently exist, where confidential information has manifested itself in a way that we believe has adversely affected the player,” Clark said. “Rest assured, it is something we are very sensitive to and something we are concerned enough about to make sure that it’s front and center.”